By way of use, foam parts for vehicle seats, which serve as upholstery for the seat structure and are to offer the user of the vehicle seat as good a seating comfort as possible, are known. The seat upholstery mostly comprises a foam part for the seat cushion and a foam part for the seat back, which is separate from the former. Each of the two foam parts has a central region and two side panels. In the case of a foam part for the seat cushion, the central region of the foam part supports the buttocks and the rear sides of the thighs of the occupant of the vehicle seat in the downward direction, while the two side panels laterally bear on in each case one thigh and, on account thereof, may absorb transverse forces acting on the occupant, in particular when cornering. In the case of a foam part for the seat back, the central region of the foam part supports the back of the occupant in a rearward direction, while the two side panels laterally bear on the back and, on account thereof, may absorb transverse forces acting on the occupant.
EP 1 068 094 B1 discloses a foam part having for increased comfort a plurality of mutually adjacent tubular portions which are molded onto a main body of the foam part and extend upward in a substantially perpendicular manner to the seat face away from the main body. As the occupant sits down, the tubular portions are initially compressed while the main body is only insubstantially deformed. It is only after significant deformation of the tubular portions that the main body is more intensely compressed. On account thereof, a dual-stage behavior with progressive upholstery hardness is achieved while sitting down.
Dual-zone foams in which by way of use of various foam materials the central region is configured so as to be softer than the side panels are known from the prior art. On account thereof, the seating comfort is to be increased on the one hand, and the lateral support for the user is to be improved on the other hand. To this end, cut foam supports are often used in the central region and hard foam inserts are used in the side panels. In order to avoid submarining of the user under the lap belt in the event of a crash, an anti-submarining function is often provided by an additional component made from a granulated foam material, for example EPP (expanded polypropylene). The additional components mentioned increase costs and reduce durability of the foam parts. Moreover, foam thicknesses are limited in terms of thinness.
A foam part having a first region of foam of a first composition and a second region of foam of a second composition is known from WO 01/74557 A1, wherein a meshwork of polyethylene, jute, gauze, non-woven material or the like is disposed between the first and the second region. However, this foam part does not meet the highest requirements in terms of comfort while sitting down, in particular not when a very soft upholstery layer is desired when initially sitting down. A comparable upholstery construction is also known from WO 2010/102785 A2.
A combination of tubular portions, as is known from EP 1 068 094 B1, and a horizontal separation plane between a first region of the foam part having a first composition and a second region of the foam part having a second composition, as is known from WO 01/74557 A1, is considered impossible to produce. Avoiding air pockets which compromise quality is considered to be impossible to achieve. Likewise, rupturing of the foam part in the region of the separation plane is suspected during demolding of the tubes, in particular when the tubes are continuously hollow for the purpose of seat air-conditioning and a separating non-woven material in the separation plane has to be correspondingly perforated.